A trade-off between natural and acquired antibody production in a reptile: implications for long-term resistance to disease.

Vertebrate immune systems are understood to be complex and dynamic, with trade-offs among different physiological components (e.g., innate and adaptive immunity) within individuals and among taxonomic lineages. Desert tortoises (Gopherus agassizii) immunised with ovalbumin (OVA) showed a clear trade-off between levels of natural antibodies (NAbs; innate immune function) and the production of acquired antibodies (adaptive immune function). Once initiated, acquired antibody responses included a long-term elevation in antibodies persisting for more than one year. The occurrence of either (a) high levels of NAbs or (b) long-term elevations of acquired antibodies in individual tortoises suggests that long-term humoral resistance to pathogens may be especially important in this species, as well as in other vertebrates with slow metabolic rates, concomitantly slow primary adaptive immune responses, and long life-spans.